What I remember from Jouke
's demo at the Perl Mongers Amsterdam
meeting last month, was that the text on the button is the default phonetic string passed to the speech synthesizer, but that you can override it. This was e.g. particularly needed for Jouke's name, which is pronounced "jauwku" rather than "jooki" (hope I got that right ;-).
The quality of speech is actually very dependent on the speech synthesizer used. We heard some examples from very hard to understand, to a Flemish speakng female voice that was hard to differentiate from real.